1. Field of the Invention
The invention relates to a device that generates a heat release rate waveform of a compression self-ignition internal combustion engine, typically, a diesel engine, and a system that diagnoses an actual combustion state by utilizing the generated heat release rate waveform.
2. Description of Related Art
As is conventionally known, in a diesel engine (hereinafter, which may also be simply referred to as engine) that is used as an automobile engine, or the like, a control map is generated by obtaining suitable values of various control parameters, such as a fuel injection amount, based on an engine operating state that is determined on the basis of a rotation speed and load of the engine through an experiment or simulation, and these are stored in an engine control electronic control unit (engine ECU). The engine ECU is configured to control the engine while referencing suitable values on the control map.
When the control parameters are corrected on the basis of the engine operating state, it is desirable that a reaction state of fuel in a cylinder (for example, ignition timing, or the like, of fuel; hereinafter, which may also be referred to as combustion state) be recognized and the control parameters be corrected accordingly such that a desired reaction state is obtained.
One of means for correcting the control parameters on the basis of the reaction state of fuel in the cylinder in this way is known as described in, for example, Japanese Patent Application Publication No. 2011-106334 (JP 2011-106334 A), in which a heat release rate waveform at the time of combustion is obtained and then the control parameters are corrected such that the heat release rate waveform becomes an ideal waveform.
However, in an existing method of generating an ideal heat release rate waveform, sufficient accuracy based on an in-cylinder environment, such as an in-cylinder gas temperature, is not obtained, and sufficient reliability is not obtained, for example, when an actual combustion state is diagnosed by utilizing the ideal heat release rate waveform.
The inventors of the invention considered the reason for that. The inventors focused on the fact that, in the existing technique, it is a cause of the above inconvenience that the in-cylinder gas temperature is uniformed, that is, the overall in-cylinder gas temperature is regarded as being uniform, and the combustion state (heat release rate waveform) is determined on the basis of the in-cylinder average gas temperature by treating the entire in-cylinder as one combustion region. That is, the inventors focused on the fact that temperature fields that significantly deviate from the in-cylinder average gas temperature may be present in the cylinder and these temperature differences cause a deviation, or the like, of ignition timing, and become an obstacle to determine an accurate combustion state (generate the ideal heat release rate waveform). The inventors found that it is effective to increase the reliability by dividing the inside of the cylinder into a plurality of regions and a combustion state is determined for each of these divided regions.
Japanese Patent Application Publication No. 2011-58377 (JP 2011-58377 A) describes estimating an in-cylinder gas temperature in view of the fact that a heat loss of in-cylinder gas varies among the regions inside the cylinder. However, in order to highly accurately define the combustion state inside the cylinder, it is insufficient to just take a heat loss into consideration.